This invention relates to high-speed printers and more specifically, it relates to a sheet-conveying device that can output paper in multiple directions.
Electrophotographic printing and reproduction devices are well known. Typically, a photoconductive member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive member in areas corresponding to the background of the document being reproduced and creates a latent image on the photoconductive member. Alternatively, in a laser-beam printer or the like, a light beam is modulated and used to selectively discharge portions of the photoconductive member in accordance with image information. With either type of apparatus, the latent image on the photoconductive member is visualized by developing the image with a developer powder commonly referred to as xe2x80x9ctoner.xe2x80x9d Most systems employ developer, which comprises both charged carrier particles and charged toner particles that triboelectrically adhere to the carrier particles. During development of the latent image, the toner particles are attracted from the carrier particles by the charged pattern of image areas on the surface of the photoconductive member to form a visualized toner image on the photoconductive member. This toner image is then transferred to a recording medium such as paper or the like for viewing by an end user. Typically, the toner is fixed to the surface of the paper through the application of heat and pressure.
Following the successful reproduction of one or more documents in this fashion, it is often desirable to perform one or more of a variety of post-processing functions on the printed documents. For example, a piece of paper that has received an image may need to be decurled, embossed, perforated, slit, rotated, or stacked. The user may also want to use a variety of finishing applications such as staplers, tape binders, perfect binders, stitchers, and signature booklet makers. These applications require output to be in a particular orientation for proper operation of the equipment.
Accordingly, a need has been recognized for post-image transfer modules capable of performing any of a wide variety of post-processing functions using the same base document handling hardware, but also releasably receiving one or more post-processing modules that perform particular post-processing functions.
Further, some printing systems may output sheets two at a time in addition to, or instead of one at a time. This is known in the art as xe2x80x9ctwo-upxe2x80x9d or xe2x80x9c2-upxe2x80x9d delivery. One way to increase the speed of the printer, without increasing the speed of the xerographic module, is to print two-up. Printing two-up involves printing two images side-by-side on the same large sheet (11xc3x9717 for example). Then, after the images are transferred to the sheet, the sheet is fed into a slitter module, which slits the sheet into two smaller sheets (8.5xc3x9711). This method effectively doubles the output speed of a printer. The images on each side of the sheet can either be duplicates or prints from separate jobs.
However, printing two-up creates problems after the slitting has occurred because now there are two sheets traveling side-by-side through the paper path. In order to get the two sheets into a single stream so that they can be handled by conventional finishing equipment, a sheet-conveying device having multiple outputs is often used. A traditional sheet conveying device having multiple outputs accepts the two sheets on input, slows them down until they hit a fixed wall, and then drives the sheets out 90xc2x0 from the input direction. Thus, the sheets exit the sheet-conveying device having multiple outputs one after the other.
Problems exist with traditional sheet sequencers and path controllers. First, traditional sheet sequencers often require manual setups of the fixed wall so that the sheet conveying device having multiple outputs can handle the correct sheet size and weight. Thus, varying paper sizes or weights in the same job cannot be handled reliably. Second, using a fixed registration wall causes the output of the sheet conveying device having multiple outputs to be edge registered. A large number of finishing devices request center registered input, and thus could not be supported with the existing system. Third, existing sheet-conveying device having multiple outputs have been traditionally unreliable. Because of their manual adjustments, they often must be tweaked between jobs for the prints to run properly. Also, because the sheets are being pushed into a registration wall, there exists the possibility of sheet damage, especially in lightweight papers.
Further, regardless of whether two-up printing is used, various factors go into the consideration of their printing system set up. One customer may want the printing and finishing modules to be arranged in a single line. Others may way want an L-shape or reverse L-shape. It would be useful for a customer to have greater flexibility when setting up a new printing system or when modifying an old printing system, such as by adding new modules or replacing old ones.
Embodiments include a method of changing the direction of travel of first and second sheets exiting a device in a two-up configuration without using a registration wall, which includes sensing a trailing edge of the first sheet and a trailing edge of the second sheet; accelerating the first sheet in a first direction with a first pair of drive rolls; accelerating the second sheet in the first direction in tandem with the first sheet with a second pair of drive rolls; decelerating the first sheet and the second sheet until each of the first sheet and the second sheet substantially stop travelling in the first direction; retracting the first pair and second pair of drive rolls; extending a third pair and a fourth pair of drive rolls; accelerating the first sheet to a first speed in a second direction oriented approximately 90xc2x0 to the first direction with the third pair of drive rolls; accelerating the second sheet to a second speed in a third direction with the fourth pair of drive rolls.
Other embodiments include a sheet conveying device having multiple outputs for sequencing two approximately identical sheets, each sheet having a leading edge and a trailing edge, wherein the sheets arrive in a two-up configuration, and wherein the sheet conveying device having multiple outputs has no registration wall, which includes a first pair of rolls; a second pair of rolls; a first shaft about which the first pair of rolls and the second pair of rolls rotate; a first servomotor operably connected to the first shaft, wherein the first servomotor rotates the first shaft; a third pair of rolls; a second shaft about which the third pair of rolls rotate, the second shaft oriented at an angle approximately 90xc2x0 relative to the first shaft; a second servomotor operably connected to the second shaft, wherein the second servomotor rotates the second shaft; a fourth pair of rolls; a third shaft about which the fourth pair of rolls rotate, the third shaft oriented at an angle approximately 90xc2x0 relative to the first shaft and approximately parallel to the second shaft; a third servomotor operably connected to the third shaft, wherein the third servomotor rotates the third shaft.
Still other embodiments include a method of changing the direction of travel of a sheet exiting a device without using a registration wall, and without rotating the sheet, which includes sensing a trailing edge of the sheet; accelerating the sheet in a first direction with a first pair of drive rolls; decelerating the sheet using the first servomotor until the sheet substantially stops travelling in the first direction; retracting the first pair of drive rolls; extending a second pair of drive rolls; and accelerating the sheet in a second direction oriented approximately 90xc2x0 to the first direction with the second pair of drive rolls.
Still other embodiments include a multi-path sheet conveying device having multiple outputs, which includes a first sensor located for detecting when a trailing edge of a first sheet passes the first sensor; a controller operably connected to the first sensor; a first shaft; a first pair of rolls rotatably connected to the first shaft; a first servomotor operably connected to the first shaft and to the controller, wherein the first servomotor rotates the first shaft; a second shaft oriented at an angle approximately 90xc2x0 relative to the first shaft; a second pair of rolls rotatably connected to the second shaft; and a second servomotor operably connected to the second shaft and to the controller, wherein the second servomotor rotates the second shaft.